1. Field of the Invention
This invention pertains to LED lead frame assemblies. More particularly, the invention relates to an improved LED lead frame structure having a thermally conducting, electrically insulating material that enhances both the thermal conduction and structural integrity of the assembly while allowing for the presence of a UV-resistant soft encapsulated material and an integral ESD device.
2. Discussion of the Art
A standard 5 mm light emitting diode (LED) package generally includes a hard plastic encapsulant material, which supplies a high degree of mechanical stability to the lead frame structure. The encapsulant allows for the manipulation and bending of the lead frame leads for solder configuration.
Various polymers have successfully been used over the years by different manufacturers as the plastic encapsulant, particularly in connection with the packaging of red and green LED products. These polymers are not generally subject to ultraviolet damage such as color centers and color shift. Suitable polymers used in the past include cycloalaphatics, PMMA, epoxies and polyurethanes.
With the invention of white LEDs and the use of gallium nitride material therein, ultraviolet light at 360-420 nanometers presents new obstacles in connection with the packaging of white light LEDs semiconductor products. For example, gallium nitride and other semiconductor materials, such as silicone carbide, emit ultraviolet light, which degrades many of the above-mentioned polymers typically used in the prior art LED assembly processes. Further, electrostatic discharge (ESD), generally associated with the handling of any LED structure including white light LEDs, induces electrical energies that damage or destroy the structures. In addition, higher power devices are presently being developed for the LED industry thereby necessitating packaging that is capable of withstanding the higher power output.
In view of its UV resistance, it is desired to use silicone as an encapsulant material in the assembly package. But the softness of silicone presents structural, mechanical, and assembly problems. More particularly, its softness does not supply a high degree of stability to the conventional LED lead frame assembly package typically used in high volume manufacturing, where lead tie bars are removed.
Thus, there exists a need for improved packaging for an LED lead frame assembly that optimizes the thermal performance of the package, allows for the presence of an encapsulant material that is UV-resistant, includes integral ESD protection, and supplies a high degree of structural and mechanical integrity to the LED lead frame assembly.
A new and improved semiconductor device packaging assembly is provided. Briefly, in accordance with one embodiment of the present invention, the packaging assembly employs a light-emitting semiconductor and input terminals connected to the light-emitting semiconductor for energizing the light-emitting semiconductor to emit light. Thermally conductive material in the assembly forms a thermally conductive path for dissipation of power out of the input terminals when the light-emitting semiconductor is energized.
A principal advantage of the present invention is that an LED lead frame assembly is disclosed that optimizes the thermal and mechanical performance of the package.
Another advantage of the present invention is that a thermally optimized lead frame assembly for LEDs is provided that enables integral ESD protection.
Still another advantage of the present invention is that an LED lead frame assembly is disclosed that provides a mechanical structure, which in turn allows for the use of soft encapsulant materials in the frame assembly.
Still another advantage of the present invention is that thermal performance of an LED lead frame package is optimized by thermal conductive bonding of the leads.
Another advantage of the present invention is that an integral ESD device is disclosed that can be used in connection with both generic semiconductor and capacitor manufacturing and packaging structures.
A further advantage of the present invention is that a low cost assembly structure, which uses a paradigm change, for an improved lead frame packaging assemblies is disclosed.
Another advantage of the present invention is that a method of structural enhancement of a LED package when using a soft encapsulant material such as silicone is disclosed.
Still another advantage of the present invention is that a lead frame assembly structure is disclosed, which can be used in the mass production of LEDs, laser diode devices, and other semiconductor and capacitor technologies.